Basic Bog Filter construction
• Bog Filter surface area should be no less than 10% the surface area of the pond, up to 20% or more if you have a large fish load, and space permits.
• Bog Filter should be approximately 12 inches deep.
• Water should enter from under the gravel, using an under gravel module with cleanout (The Aquascape Centipede™ Module with Snorkel™ Vault works excellent for this.)  clean-out vault allows for easy sediment removal, reducing the need for costly and invasive dredging.

• Fill Bog Filter with larger 2”-3” rock, pea gravel as a planting media and a few large specimen size rocks to naturalize the feature.
• Aquatic and marginal plants should be planted directly into the gravel and include the entire undisturbed root-ball which will contain soil.
• Water flows up through the gravel and overflows via a waterfall back into the main pond.

The Differences between A Water Garden, A Traditional “Koi Pond” and their filtration systems:

The first thing you need to know is that a “Koi pond” filter system is completely different than a Biological Bog filtration system for a water garden, although they do have some similarities. Both “Koi pond” filters and bog filtration systems use biological filtration to maintain water quality. A biological filter is simply a device or area where living nitrifying bacteria can attach themselves. The bacteria eat the excess nutrients such as fish waste and organic matter from the water before it can become a food source for algae in the pond, thus starving the algae out of the water. In my opinion both water features have there place. The major difference between a “Koi pond” biological filter and a bog filtration system are the size and location of the filters.


The typical “Koi pond” is a concrete or liner bottom pond with a bottom drain that uses a large “swimming pool” style biological filter outside the pond. They do an excellent job of filtering the water, and providing a sterile environment for show quality Koi to live in. I’ve seen them, and that's my point! They are big, and you see them!

 

 

Now, Koi are some of the most beautiful and fun pets you could ever have! Some people get so “into” the hobby of owning Koi that they literally spend thousands of dollars for a single fish. The Koi are the star of the "Koi pond".  Well, for the kind of money that is often spent on a show quality Koi, I would create a sterile environment for them to live in, too. I could not image spending thousands of dollars on a show quality Koi, and chancing them scraping up against a rock or other sharp object in the bottom of my pond.

A water garden on the other hand is designed to mimic Mother Nature in both appearance and function. It should consist of many of the same elements that Mother Nature puts in her water gardens ~ fish, snails, frogs, tadpoles, beneficial bacteria, plants, rocks, gravel, and sometimes even dirt and sand! There will be birds bathing at the pond’s edge, dragonflies & butterflies fluttering nearby,  fish jumping up to catch a bug, blooming lilies floating on the waters surface, cattails swaying in the breeze, and everything else you would see in a pond or lake in the wild. You’ll want to have waterfalls, maybe a stream, varying depths in the pond and there will be underwater “caves” for the fish to swim into to protect themselves from predators. The Koi or goldfish are an integral part of, but only one part of the whole picture.

 

 

Live plant roots act as filters, absorbing nutrients from the water before algae has a chance to. The fish also like to nibble on the plant roots. And, after a few years, if the plants get too large for their location, they can be removed for dividing easily since they are planted in gravel.

 

The bog filtration system then empties freshly filtered water via a trickling waterfall into the pond or water garden. In my opinion, a natural, hidden filter that becomes a waterfall is far more beautiful to look at than a big “swimming pool” type filter. Just remember that water quality is always of utmost importance. Even a bog filtration system requires maintenance, and a clean pond is a happy & healthy pond.

Plants Used In Bog Filtration

A flourishing bog filter helps stabilize water chemistry, removes toxic compounds, keeps water clear and fish happy. The bog is a wonderful addition to any pond system or as a stand alone water feature. Wetland or bog filters are best constructed in an up flow design which reduces clogging and facilitates easy cleaning.  Bio-Mass is key ~ A pound of bog is required to prevent a pound of algae. Plants should be selected that actively grow at different times, that root to different depths and that have different plant structures.
 

Excellent Plants for the Bog may include:

Arrowhead Sagitaria (zone 4-6) Summer Bloomer. Bulbing root system stores(nitrogen, potassium & phosphorous)

Canna (zone 8-10) Summer Bloomer. A bog’s best friend. This plant is a biomass factory and has amazing beauty and structure. A heavy feeder on (nitrogen, potassium & phosphorous) from April through September.

Cattails (zone 3-5) Summer Bloomer. are vigorous growers and have deep roots.

Creeping Jenny (zone 5) Spring Bloomer.

Daylily - Spring through Summer Bloomer. Surprisingly, water is the best fertilizer for daylilies. They are an excellent nutrient feeder and grow well in the shallow areas of a bog garden. Daylily come in a variety of colors and blooming times for a long lasting color in your garden.

Eyed Grass (Yellow & Blue) (zones 5-7) Spring Bloomer.

Iris - (zones 4-6) Summer Bloomers.
Common water iris. (Louisiana Iris) Great variety in colors and styles. Plant habit is spreading and untidy appearance.
Japanese variegated water iris is a strong grower late spring through fall. Iris are good at removing both nitrogen and phosphorous.
Siberian Iris are preferred for their strong, clumping habit. Most growth spring and summer but use potassium and phosphorous in summer and fall for energy storage for next year’s bloom.

Kaffir Lily (zone 7) Fall Bloomer. A bulbing lily with watermelon red flowers. Grows in cooler temps of spring and fall. Small top growth controlled.

Lobelia Cardinalis (zones 5-7) Fall Bloomer. Beautiful late summer bloom. Nice color diversity. Heavy potassium user.

Marsh Marigold (zones 2-4) Spring Bloomer. A fast growing cool temperature plant. Begins growing very early in spring producing flowers by early March and continues through April, often re-blooms in the fall when weather cools. Medium root depth and actively feeds when most plants are dormant.

Pickerel Rush (zone 3-6) Summer Bloomer. Strong summer growth and bloom. A spreading habit with a shallow root system. A strong feeder on the total nutrient system. Blue Pickerel Rush is very hardy in our area, with a long bloom season.

Rain Lily (zone 6) Fall Bloomer. Late summer and fall grower. This bulb plant has a small controlled top growth but a dense vigorous root system with storage bulbs. Strong user of phosphorous and potassium.

Rush - Variegated Striped Rush (zone 5-6) Summer Bloomer. Evergreen and continues to grow almost year-round strongest growth in summer. Roots are shallow and need oxygen. Open habit allows for under story growth.but has a large vigorous root system feeding its bulbs. Very

Slough Sedge (zone 4) Very prolific, yet clumping. Grows to 5’ high in bogs. Deep rooting habit. Bio-mass. Strong user of potassium, sulfur, calcium and sodium. Somewhat salt resistant.

Society Garlic (zone 7) Summer Bloomer. Strong summer growth. Love phosphorous.

Star Grass (zone 7) Summer Bloomer. Very controlled, medium root depth, summer fall growth. Grasses are strong feeders of potassium and sulfur.

Thalia (zone 6) Summer Bloomer. Very deep rooted. Open stem structure allows for very diverse under story growth. Summer blooming. Large storage roots.

Water Forget-Me-Not (zone 3) Spring Bloomer. Vigorous low grower. Shallow rooted. Easily pruned. Blooms from March through October.

Yellow Monkey Flower (zone 6) Spring Bloomer. Early spring growth and bloom. Deep root system.


There are big differences between a water garden and a traditional “Koi pond” and the sad fact is, many “Koi” keepers don’t understand that there are different but equally appropriate ways to have live fish in the landscape. Next time you are purchasing a Koi or Goldfish, an aquatic plant, or getting “free” advice from someone that tells you that “you can’t put rock, plants, and fish together in the same body of water”, just smile and politely let them know that you have a water garden and it’s working just beautifully.



Disclaimer: Information is deemed reliable, but not guaranteed…...........Water quality testing is always of utmost importance and regular pond cleaning & maintenance is always recommended.